As is well known, a butterfly valve, for example, opens and closes a flow pass and adjusts a flow rate by rotating a support shaft that supports a circular plate-shaped valve element.
A common butterfly valve is typically provided with a rubber-made valve seat in order to improve the sealing efficiency when the valve is closed. However, as the valve element slides along the valve seat when the valve is opened and closed, the valve seat is abraded and the abrasion powder is possibly mixed in a distributed product as a foreign matter. Further, in the case of a large-diameter valve, a load due to the sliding between the valve element and the valve seat is large, and this possibly makes the opening and closing behavior of the valve unstable.
As a butterfly valve that is effective to such a problem, it is envisaged that the valve element is removed from the valve seat by positioning the valve shaft that supports the valve element in an inclined manner, and the valve element is rotated in this state by the valve shaft (see Patent Documents 1 to 3). With this configuration, it is possible to suppress the sliding between the valve element and the valve seat.
Further, in a fluidized bed apparatus that performs processes such as granulation, coating, and drying while a powder and granular material is floated and fluidized within a fluidized bed container to form a fluidized bed, a circular plate-shaped air distributor configured by a perforation plate (also referred to as a perforated plate) is disposed at a bottom section of the fluidized bed container, and a fluidized air is introduced into the fluidized bed container via the air distributor. Considering the convenience and the efficiency in cleaning of an interior of the fluidized bed container, a mechanism for inverting the air distributor is often provided (see Patent Document 4).